Desktop computer: Installing a keylogger, for example, is cheap and require skills like “can purchase a cheap and simple technical part” and “can plug in a USB”, which are skills you can assume a CS student will possess.

Laptop: Same, but have to open the laptop and install a less standard straightforward loggrr on the internal cable. This require more effort and patience.

Phone: I have no idea, and I am a computer scientist who spends time thinking about this. I mean, all phones can be opened with corresponding equipment, and the touch screen is connected to the internal computer with a cable, but they differ in details per model and the space to work with is tiny. The research investment is significant and model dependent. Meaning, the effort cost is quite high and they’d need extremely strong motivation.